In Volume 7's Introduction of Characters that Don't Need to Reappear - Part 5 Anbe gives brief description about Yuka Nishimura and Tomomi Mochizuki: Kiyomi's club activity underclassmen characters who are far away from the regular character.

As to why they have names: (note: This introduction appears after both girls' first appearance)Before Ika Musume was published, I was an assistant for over two years, creating storyboards weekly for a badminton manga with them as the main characters. That badminton manga didn't do so well and I drastically drew a different manga, that is Ika Musume.